The present invention relates to syringes, and particularly to a safety syringe having a simple structure so that it can not be reused.
With reference to FIGS. 1 to 4, the prior art syringe includes a syringe 10, a seat 20 and a push rod 30.
The syringe 10 is a round cylinder penetrated from the front end to the rear end. A stop wall 11 is radially arranged to be at an inner wall of the syringe 10 near the front end thereof. An annular first unidirectional buckling lip 13 is installed at an inner wall of the rear side of the syringe 10.
A front end of the seat 20 is a sleeve 21 for connecting a needle 40. A seat has a liquid flow channel 22 which penetrates the front and rear ends of the syringe and at an axial center thereof. A rear end of the liquid flow channel 22 is formed with an unidirectional buckling chamber 23. An outer wall of the seat 20 is formed with an annular groove 24 with respect to the first lip 12 at a front end of the syringe 10.
The front end of the push rod 30 has a rod head 31. A plurality of connecting points 32 serves for connecting the push rod 30 with he rod head 31 so as to be formed as a breaking section 33 by which the rod head 31 is broken after use. The rod head 31 has a second water-stop ring 34. A front end of the rod head 31 has a tapered buckling head 35.
By above mentioned structure, the seat 20 and rod head 31 of the push rod 30 can enter into the syringe 10. Then, the seat 20 can be pushed into the first lip 12 at the front end of the syringe 10 so as to be buckled to a front end of the syringe 10. The sleeve 21 at a front end of the seat 20 protrudes from the front end of the syringe 10. Thereby, needle 40 can be screwed into the syringe 10 (referring to FIG. 1). When the push rod 30 is pushed to a foremost end, the buckling head 35 at the front end of the rod head 31 can be pressed into the unidirectional buckling chamber 23 at a rear end of the seat 20 (referring to FIG. 2). Next, the push rod 30 is pulled backwards and at the same time, the seat 20 is retracted so that the needle 40 can be placed into the syringe 10 (referring to FIG. 3). Further, the needle 40 is retracted to be stored in the syringe 10. Then the rod head 31 is broken to separate from the push rod 30 (referring to FIG. 4). Thereby, the syringe 10 can be not reused. Thereby, the object of safety is achieved.
However when the push rod 30 is pushed to the foremost end (referring to FIG. 5), the buckling head 35 at the foremost is plugged into the unidirectional buckling chamber 23 at the rear end of the seat 20 so that the seat 30 is firmly secured to the push rod 30. When the push rod 30 is pulled backwards, the seat 30 can be pulled out at the same time. Thereby, the needle 40 is stored in the syringe 10. Thus, the buckling head 35 at the front end of the push rod 30 is easily plugged into the unidirectional buckling chamber 23 at the rear end of the seat 20. To cause that the buckling head 35 will not separate from the unidirectional buckling chamber 23 and can drive the seat 20 to move backwards when the push rod 30 moves backwards. A high precision is necessary so that it is difficult to make, maintain and prepare a mold. As a result, the cost is increased Moreover, to control the precision of the buckling head 35 and the unidirectional buckling chamber 23 is difficult so that the quality can not be well controlled.
Further, a front end of the liquid flow channel 22 of the seat 20 has a space which would accumulates drugs therein so that when the push rod 30 is pushed to the foremost end, part of the drug will flow into the liquid flow channel 22. The amount of the drug is over the international standard, 0.075 ml.
Accordingly, the primary object of the present invention is to provide a safety syringe, which can improve prior art defects as mentioned above.
To achieve above objects, the present invention provides a safety syringe, wherein plurality of axial slits are formed in the outer wall of the unidirectional buckling chamber of the seat. An inner wall of the unidirectional buckling chamber has a second unidirectional buckling lip. A buckling head at a front end of the rod head of the push rod is installed with a unidirectional buckling lip; the third unidirectional buckling lip is installed with a plurality of slits so that the third unidirectional buckling lip is elastic. Thereby, by the axial slits of the unidirectional buckling chamber and the slits of the third unidirectional buckling lip, when the push rod is pushed to a foremost end, the buckling head at the front end of the rod head is pushed into the unidirectional buckling chamber at the rear end of the rod head of the push rod. The buckling head at the front end of the rod head of the push rod is extended with an axial strip. When the push rod is pushed to a foremost end, the axial strip is inserted into the liquid flow channel of the seat, the liquid in the liquid flow channel is pushed out so as to reduce the residue of the liquid so as to match the international standard.
The various objects and advantages of the present invention will be more readily understood from the following detailed description when read in conjunction with the appended drawing.